Neonatal and long-term outcomes of very low birth weight infants from single and multiple pregnancies

The revolution in artificial reproductive technologies has resulted in a dramatic rise in the incidence of multiple pregnancies. Many of these infants are born prematurely, often extremely so. Consequently, perinatal morbidity and mortality are highly correlated with plurality. The primary mechanism for this increased risk is prematurity. Studies of the relationship between plurality and outcome are frequently hampered by major differences in case mix between singletons, twins and high multiples. For example, high multiples tend to receive earlier prenatal care, receive more antenatal steroids, are more often delivered by Caesarean section and more often suffer from respiratory distress syndrome. However, recent studies that appropriately account for relevant confounding variables have suggested that very low birth weight infants from high multiple pregnancies are at excess risk for mortality when compared with twins and singletons. This article reviews the current available evidence.